System for continuous operation of series connected hermetically closed centrifugal separators



mujfiwr Dec. 6, 1960 F. T. E. PALMQVIST ETAL 2,963,219

SYSTEM FOR CONTINUOUS OPERATION OF SERIES CONNECTED HERMETICALLY CLOSEDCENTRIFUGAL. SEPARATORS Filed Apri122, 1957 2 Sheets-Sheet 1 IN VENT 0R5lzfaallz'rer :To/fmamz ATToR N E Y Dec. 6, 1960 F. 'r. E. PALMQVIST ETAL 2, 1

SYSTEM FOR commuous OPERATION OF SERIES CONNECTED HERMETICALLY CLOSEDCENTRIFUGAL SEPARATORS Filed April 22, 1957 2 Sheets-Sheet 2 Fig. 5

' 0 c0 66 (P (P TToRNE V5 United States Patent SYSTEM FOR CONTINUOUSOPERATION OF SE- RIES CONNECTED HERMETICALLY CLOSED CENTRIFUGALSEPARATORS Fredrik Teodor Emanuel Palmqvist, Solna, and Walter Holfmann,Lidingo, Sweden, assignors to Aktiebolaget Separator, Stockholm, Sweden,a corporation of Sweden Filed Apr. 22, 1957, Ser. No. 654,213

Claims priority, application Sweden Apr. 26, 1956 12 Claims. (Cl. 23318)The present invention relates to a system for continuous operation of atleast two hermetically closed centrifugal separators which work inseries and are controlled independently of each other.

A system of the kind stated above may be used in various industries forcontinuous manufacture of a product, where a component must be separatedfrom one or more other components in separate steps. This is the case,for instance, when refining fatty oils, where the oil first may bedegummed, then neutralized with alkali, then decolorized with alkali,and washed with water in order to be freed from its content of soap, andfinally bleached and deodorized. Each one of the above operations isnormally followed by a separating step.

Another similar industrial field is the production of antibiotics, forinstance penicillin, where, in order to attain the best possiblerecovery (maximum yield) of the penicillin, it is necessary to makerepeated extractions of the raw material with a suitable agent, forinstance amyl acetate. After each extraction step, the extract isseparated from the aqueous phase.

A third important industrial field is soapmaking. Here it is necessaryto separate the soap from spent lye after graining and from nigre afterfitting. Graining as well as fitting may be effected repeatedly in orderto attain a high quality of soap.

In the three industrial fields mentioned above as examples, it isdesirable to operate in a totally closed system, for reasons which willnow be described.

When refining fatty oils, it has been found that an oxidation of the oilimpairs its quality. A measure for the degree of oxidation is obtainedby determining the peroxide number of the oil and preferably thecarbonyl content of the oil, both of which are low in an oil of goodquality. Further, it has been found that a fatty oil refined in atotally closed system has a better keeping quality than an oil refinedin an open or partly open system, even though the two oils afterrefining (including bleaching or deodorizing) have the same peroxidenumber. In refining methods which use an extraction agent for the oil,for instance naphtha or hexane, it is also desirable to avoid losses ofthe extraction agent because of evaporation.

In the preparation of penicillin, it is of primary importance to preventevaporation of the extraction agent, particularly as the extraction ofthe penicillin is carried out in several steps.

In soapmaking, it is desired to avoid contact with the 2,963,219Patented Dec. 6, 1960 ICC air for at least two reasons, namely,oxidation can darken the soap, and admission of air into the soap masscauses dilficulties when it comes to separating the neat soap from thenigre after fitting. Further, the subsequent milling, etc., may undercertain circumstances become extremely difficult if the soap containsair. In addition, open systems have the inconvenience that the soapsolidifies at open points, for instance in the receiving vats at theoutlets of the separator, by being cooled. This presents difliculties inthe passage of the soap through the system.

On the other hand, when it is attempted to avoid these inconveniences bymaking the system totally closed (connecting successive separatorsthrough closed lines), then new problems are encountered. That is, inorder to allow the closed centrifugal separators to Work satisfactorily,the boundary levels adjusted in the separators must not be displacedowing to pressure variations arising in the closed system andpropagating through it. These variations must therefore be preventedfrom asserting them selves from separator to separator in the closedsystem, so that the various separators can be controlled individuallywithout disturbing each other.

The principal object of the present invention is to provide a systemwhich overcomes the above-noted difficulties.

According to the invention, an outlet of one centrifuge is connectedwith the inlet of a second centrifuge by a, closed line provided with apumping means of a capacity which is at least equal to the amount ofmedium maximally discharging per unit of time from the first centrifuge.Also, a controllable throttle member or valve is provided in an outletfrom the second centrifuge; and in the closed line between thecentrifuges is provided a device for maintaining constant pressure in apart of the line, preferably between the first centrifuge and thepumping means, as calculated in the fiow direction. The closed linebetween the separators includes the device or devices in which thevarious treatments between the separators are to be carried out. Thesedevices are, of course, of a closed design. The controllable throttlingmember or valve, may consist of exchangeable throttle discs; but in acontinuously operating plant it is, of course, desirable that thethrottling member consist of a throttle valve which is controllableduring operation and can be manually or automatically operated.

As the pumping means employed must have a capacity which is suflicientfor a maximum output in the plant, it may in normal operation be allowedto work only with a capacity below the maximum. If the soap mass orother medium flowing through the system contains a component which canbe evaporated relatively easily (for instance water) so that its vaportends to fill the spaces on the suction side of the pumping means, apositive pump may be used as the pumping means. By this is meant a pumpwhose capacity is directly proportional to the number of revolutions ofthe pump, such as a piston pump, sliding vane pump, screw pump, or gearpump. The two latter types of pump are preferred in the system accordingto the invention. As a positively working pump in normal operation willproduce, on its suction side, a vacuum which disturbs the pumping work,especially when the pump medium does not contain any easily evaporatedcomponent, a pump of a different type (for instance, a centrifugal pump)may be employed. It has proved desirable, however, to use a positivelyworking pump owing to its ability to feed the medium practicallyindependently of the counterpressure. In that case, the pump may bedesigned so that there is a certain allowable leakage between thepumping parts, or it may be provided with a return line joining thepressure side of the pump with the suction side of the pump. Thiscounteracts formation of vacuum on the suction side of the pump.

7 If the quantity flowing per unit of time through the system has atendency to vary to a certain extent, a manual control of the throttlemember in the outlet of the second centrifuge will not be satisfactory.In that case a conventional type of valve adapted to keep constantpressure may be provided in the outlet of the second centrifuge. Suchvalve must keep constant pressure at its inlet side, that is, in thecentrifugal outlet proper. For the same reason, it may be desirable toinsert a similar valve in the above-mentioned outlet of the firstcentrifuge as well as in any other outlets of the centrifuges.

In the above case, when a positively working pump is provided with areturn line, it may be advantageous to insert in the return line a valve(such as a spring-loaded valve) which opens at a determined pressuredifference between the pressure side and suction side of the pump. Thismakes it possible to ensure that the medium is supplied to the secondcentrifuge at a certain minimum pressure.

When using a positively working pump with a return line, according to analternative embodiment of the invention, the device for maintaining aconstant pressure may consist of a valve provided in the return line andwhich keeps constant pressure on the suction side of the pump. If,however, the pressure in the inlet line of the second centrifuge in thiscase should be considerably reduced because of some disturbance in theoperation, a valve keeping a constant pressure at its inlet side may beprovided in the closed line after the positively working pump and itsreturn line. The pressure drop in the second centrifuge is therebyprevented from disturbing the separation process in the firstcentrifuge.

When a valve in the return line keeps constant pressure on the suctionside of the pump, this means that the pressure in the inlet of thesecond centrifuge must be considerably higher than the pressure in theoutlet of the first centrifuge. For some reasons (e.g. sealingrequirements) this is not always suitable. This difiiculty may, however,be eliminated by providing a controllable throttle member in the closedline after the first centrifuge but before the connection of the returnline. This makes it possible to keep a considerably lower pressure onthe section side of the pump than in the outlet proper from the firstcentrifuge, so that a lower pressure can also be kept in the inlet ofthe second centrifuge.

The embodiments described above have proved suitable for use insoapmaking. However, for refining a fatty oil it is desirable to use amodified embodiment due to different conditions of operation. Thus, inthis modified embodiment no provision should be made for filling thespaces on the suction side of the pump with steam, and, further, anaccurate adjustment of the boundary levels in the centrifuge is requiredin order to prevent soapstock from being entrained with the separatedoil. In this case, it is desirable to maintain a constant supply of oilto the system and a corresponding constant dosage of the variousreagents to the oil. As a result, the system should be equipped with ameans for keeping a constant supply to the first centrifuge; it beingassumed that the pumping means consists of a positively working pumpwith a return line connecting the pressure side of the pump with thesuction side of the pump, and that the means for maintaining av constantpressure consists of a valve provided in the return line and which keepsa constant pressure on the suction side of the pump.

Further, in the closed line after the first centrifuge but before theconnection of the return line, there should also be provided in thiscase a controllable throttle member if, for reasons indicated above, itis not desired to keep a considerably higher pressure in the inlet ofthe second centrifuge than in the outlet of the first centrifuge.

According to one embodiment of the invention, the means for keepingconstant supply to the first centrifuge comprises a positive pump in theinlet line of the first centrifuge, and a throttle valve between thispump and the centrifuge. A closed line, starting from a point of theinlet line between the pump and the throttle valve, connects thepressure side of the pump with the suction side of the pump, andinserted in this closed line is a diaphragm-controlled valve which isdesigned to keep a constant pressure drop between both sides of thethrottle valve. That is, the inner diaphragm chamber of thediaphragm-controlled valve is directly connected, via this closed line,with one side of the throttle valve, while the other side of thethrottle valve is connected with the outer diaphragm chamber of thediaphragm-controlled valve via a closed line starting from a point ofthe inlet line between the throttle valve and the centrifuge.

If the system of the present invention comprises more than twocentrifuges, the above-described arrangement between the centrifuges mayrecur between the additional successive centrifuges.

The invention is explained more in detail below, reference being made tothe accompanying drawings which illustrate examples of the inventionapplied to a system for refining a fatty oil and to a system for makingsoap. In the drawings,

Fig. 1 is a diagrammatic view of a system for constant supply of fattyoil to a first separator shown in Fig. 2;

Fig. 2 is a similar view of this first separator and its closedconnection to the next separator;

Fig. 3 is a diagrammatic view of a system for making soap, whichembodies another form of the invention, and

Fig. 4 is a similar view of still another form of the invention.

In Fig. 1, 1 designates a. tank which through a line 2 feeds apositively working pump 3 inserted in the line 2. In operation, the tank1 should contain enough oil to keep the pump 3 entirely fed. This can beeffected manually or automatically, in the latter case by means of afilling device (not shown) which feeds the tank 1 and which, in aconventional manner, is controlled by the oil level in the tank. Thearrows in the various figures indicate the flow direction of the oil orother medium. The line 2 also contains a heater 4 for raising the oil tothe required temperature, and a mixer 5 in which the oil is mixed with areagent solution (for instance, water or an aqueous solution ofphosphoric or other acid) for degumming. 1f the system has no separatedegumming step, this reagent solution may be caustic soda or lye, forneutralization of the fatty acids. The water or the aqueous solution issupplied to the mixer 5 through a line 6 by means of a dosage device(not shown) of conventional type which feeds a constant amount per unitof time in spite of varying counterpressure, for instance, a pump of thegear type. From the pressure or outlet side of the pump3, a line 7 leadsback to the suction or inlet side of the pump- In this line 7 isinserted a diaphragmcontrolled valve 8, while a shunt line 9 contains asafety valve 10. Oil, which occasionally can be let through the safetyvalve 10, is thus discharged to the suction or low pressure side of thepump 3. The line 2 also contains a throttle valve 11 which inco-operation with the valve 8 is to ensure constant supply to thesubsequent separator.

The valve 8 contains a diaphragm I2 dividing the upper space of thevalve into the outer diaphragm chamber 13 and the inner diaphragmchamber 14, while the lower space of the valve is divided by a partition15 into an inlet chamber 16 and an outlet chamber 17. In the partition15 is a valve opening which is throttled by a valve body 18. A spindle19 supporting the valve body 18 is connectedto and controlled by thediaphragm 12, which is adapted to be biased by a constant force, in thiscase a spring 20 adjustable by means of a screw 21.

A line 22 starting from the line 2 opens into the outer diaphragmchamber 13 of the valve 8, while the line 7 opens into the inlet chamber16 of the same valve and via the latter chamber is in unthrottledcommunication with the inner diaphragm chamber 14. Requisite manometersare shown at 23, 24, and 25, and these may be assumed to indicate thepressures 0.2, 3.5, and 3.0 kg./cm. during normal operation. The amountof oil discharging from the line 2 may be assumed to be 2000 l./h.,while the capacity of the pump 3 may be, say, 3000 l./h. Disregardingthe liquid supply through the line 6, 2000 l./h. are supplied from thevessel 1, while 1000 l./h. go back through the line 7 to the suctionside of the pump 3.

The purpose of the system described above is that a constant pressuredrop of, say, 0.5 kg./cm. is to exist between both sides of the valve11. At a certain adjustment of this valve, a certain amount of oil isdischarged per unit of time from the line 2, independently of theabsolute magnitude of each pressure. If now the oil discharging from theline 2 meets an increased counterpressure, this pressure propagatesthrough the line 22 to the outer diaphragm chamber 13 of the valve 8.This results in the diaphragm 12 being pressed downward so that thevalve body 18 will throttle the valve opening in the partition 15. Thisobstructs the flow through the valve 8, so that a compensatingcounterpressure is built up in the chambers 16 and 14 and consequentlybetween the pump 3 and the valve 11. The diaphragm 12 is then returnedupward until it attains the state of equilibrium again. In this way, aconstant pressure drop is always ensured between both sides of the valve11 and, thus, a constant flow through it. Upon a pressure drop on thesuction side of the pump 3, the valve 8 operates in the same manner asdescribed above. The valve 8 will, of course, work in the oppositemanner in response to pressure changes of opposite kind.

According to Fig. 2, the line 2 opens into a hermetically closedseparator 26 where the oil is freed from gums and is discharged througha line 27 in which there is inserted a valve 28 serving to adjust theboundary level (neutral zone) in the separator 26. The gums leaveseparator 26 through an outlet (not shown) opening into the openatmosphere. The pressure, for instance 1.5 kg./cm. of the dischargingoil may be read on a manometer 29. In the line 27 are inserted a heater30, a positively working pump 31 and a mixer 32. Into the latter opens aline 33, through which a reagent such as caustic alkali lye may besupplied by means of a dosage device (not shown) of a kind similar tothat which feeds the line 6. A quantity of oil of 2000 l./h. passes fromthe line 2 into the separator 26 and this oil passes on through the line27 into another hermetically closed separator 34 which in its oildischarge line 35 has a throttle valve 36. By means of this valve thepressure of the discharging oil may be adjusted to a value suitable forthe boundary level in the separator 34, for instance 2.0 kg./cm. whichmay be read on a manometer 37. The soapstock separated in the separator34 is discharged through an outlet (not shown) opening into the openatmosphere. The pump 31 is, like the pump 3, assumed to have a capacityof 3000 l./h., and therefore 1000 l./h. must be forced by thecounterpressure in the separator 34 to flow back to the suction side ofthe pump through a return line 38. The pressure on the pressure side ofthe pump 31, for instance 3.0 kg./cm. may be read on a manometer 39. Aline 40, with a safety valve 41 inserted in it, is branched off from theline 38. Any oil that possibly may be let out through the line 40 iscaught by an outlet funnel 42.

In the line 38 is inserted a diaphragm-controlled valve.

43, the parts of which have the same reference numerals as correspondingparts in the valve 8. A manometer 44 is inserted on the suction side ofthe pump 31, where a constant pressure of for instance 0.2 kg./cm. is tobe maintained.

If the pressure on the suction side of the pump 31 drops below apredetermined value, which may be adjusted by changing the tension ofthe spring 20 in the valve 43, the valve diaphragm 12 and the valve body18a move downward. Consequently, an increased quantity of oil entersthrough the valve opening in the partition 15a of valve 43, until thepredetermined pressure on the suction side of the pump is attainedagain, whereupon the diaphragm resumes its state of equilibrium.

A pressure increase arising, for example, in the separator 34 propagatesthrough the lines 27 and 38 to the inlet chamber 16 of the valve 43,where it acts through the valve opening and the chambers 17 and 14 tomove the diaphragm 12 upward. The valve opening is thus throttled by thevalve body 18a so that an increased pressure is built up in the chamber16. In other words, a pressure increase in the separator 34 produces acorresponding pressure increase on the pressure side of the pump 31.After the diaphragm 12 of valve 43 has resumed its state of equilibrium,this causes the feed pressure to the separator 34 to become constantagain. At the same time, the first separator 26, being uninfluenced bythese pressure variations, discharges against the constant pressure onthe suction side of the pump 31 and thus operates without disturbancesfrom other pressure variations arising in the system.

The oil discharging through the line 35 may then be' subjected tofurther treatment required for obtaining a refined product, thearrangement between the separators 26 and 34 recurring between anyadditional successive separators.

The system shown in Fig. 3 includes a feed line 45 from a saponificationstep (not shown). The feed line 45 leads into a mixer 46 to whichgraining electrolyte is supplied through a line 47. The grained soap issupplied by means of a pump 48 to a hermetically closed centrifugalseparator 49 in which the neat soap is separated from the spent lye. Theneat soap is thereupon discharged through a line 50, which is directlyconnected hermetically in the usual manner to the rotor of the separator49, this line 50 containing a valve 51 which keeps constant pressure inthe separator outlet proper and which may be a diaphragm-controlledvalve of a design similar to the valves 8 and 43 shown in Figs. 1 and 2.A valve 51a of similar construction is also provided in line 50 andserves to keep a constant pressure at the inlet side of valve 51a. Inthe line 50 is also a gear pump 52 by means of which the neat soap isconveyed to a mixer 53. Fitting electrolyte is led into this mixerthrough a line 54. The fitted soap goes from the mixer '53 into anotherhermetically closed separator 55 from which fitted neat soap dischargesthrough a line 56 having a valve 57 and, if desired, a gear pump orscrew pump 58. The valve 57 is to keep constant pressure in the outletfrom the separator 55 and may be of the same type as the valve 51. Theother separated components from the two separators 49 and 55 (spent lyeand nigre, respectively) are discharged through lines 59 and 60,respectively, directly connected hermetically to the rotors in therespective separators. The lines 59 and 60 have valves 61 and 62,respectively, and pumps 63 and 64, respectively. The valves 61 and 62are to keep a constant pressure in the respective separator outlets. Thenig-re leaving through the line 60 is returned to the mixer 46, whereits content of soap is recovered by graining. In each of the outletsfrom the two centrifugm there is thus maintained a constantcounterpressure by means of the valves 51, 57, 61 and 62, whereby theboundary surfaces;

7 (neutral zones) between the two components to be separated in thecentrifuges maintain their positions independently of the fluctuationsthat may occur in the quantities flowing through the centrifuges.

The pump 52 is provided with a return line 65 which connects thepressure side of the pump with the suction side of the pump and in thisline is inserted a valve 66 which opens only at a determined pressuredrop between the pressure and suction sides of the pump.

In. the system of Fig. 4, the constant pressure in the line between thecentrifuges is maintained primarily on the pressure side of the pump,and the throughfiow preferably is kept constant. The centrifuges hereare shown for carbonyl compounds, had been developed with 2,4- dinitrophenyl hydrazine and alcoholic KOH. E is equal to 1 in entirelytransparent oil and increases along a logarithmic scale as the degree oftransparency is decreased. The two oils were thereupon bleached invacuum at 120' C. with 2% activated bleaching earth, whereupon peroxidenumber and carbonyl content were determined for the bleached oils aswell as the oxidation stability of these oils. The latter test waseifected by blowing through oxygen gas at C., in which test the increaseof the peroxide number after a certain time was determined. The resultsare shown in the following Table I.

Table I Analysis of lye'treated, Analysis of bleached oils washed anddried oils Time in Peroxide Carbonyl Peroxide Carbonyl hours for numbercontent number content attaining mllliequL/l e./g. at mllliequL/l 0.1g.at the per- 460 my 460 m oxide number 10 Oil mined in open plant 2. 5 1.63 0. 0 1. 94 140 Oil refined in all-hermetic plant 0. 6 1. 41 0.0 1. 60170 at 67 and 68 and the inlet to the first centrifuge is shown at 69.In the line 76 between the two centrifuges is inserted a pump 7 which isshown as a centrifugal (nonpositive) pump, although it may be a gearpump with a return line. A valve 72, which may be of the same type asthe valve 43 in Fig, 2, is provided to keep constant pressure in theline 70 on the pressure side of the pump 71. In Fig. 4, however, thevalve 72 is shown to be actuated by a manometer 73 which, through asuitable operating connection 74, controls an actuator 72a of thediaphragm type for the valve 72 so that the latter throttles the line 76if the pressure in the inlet to the centrifuge 68 rises, and vice-versa.With the conditions given above, the pressure on the suction side of thepump 71 will be kept constant, and therefore the centrifuge 67discharges into the line 70 against a constant pressure. In the outlet75 from the centrifuge 68 is a controllable throttle valve 76.

The effect of the invention as applied to refining of fatty oils isillustrated by the following examples:

EXAMPLE 1 An amount of crude rapeseed oil with a content of free fattyacids of 2.3% and a peroxide number of 0.8 mi'lliequivalent/l. wasdivided into two parts, of which one was continuously refined in asystem containing open separators, where the oil is mixed with air inthe inlet of the separators and thereupon is thrown out from the bowlinto the open separator covers, where the oil is spread like a mist andcomes into very intimate contact with air. The other half wascontinuously refined in a system comprising hermetically closedseparators which were hermetically connected together according to thepresent invention.

Both the refining plants were equipped with three separators of whichthe first was used for neutralization, the second for re-refining, andthe third for washing. Each of the plants also comprises a dryingsection operating under vacuum.

The peroxide number for the neutralized, re-refined, washed, and driedoils was determined, stated as milliequivalents peroxide per litre, andso was the carbonyl content which, owing to insufficient knowledge ofthe molecular weight of the carbonyl compounds present in the oil, wascalculated as extinction (E) per gram of oil" in ml. solvent at 460 mu(ultra violet light) in 1- cm. cell, after the red hydrazone colour,specific As appears from the table, the peroxide number and the carbonylcontent are both highest for the oil refined in the presence of air.When bleaching, the peroxide number falls to zero, while the carbonylcontent increases, evidently owing to carbonyl compounds being formedwhen the peroxides are split. The peroxide number of the lye-treated oilgives therefore an indication of how much the oil has been damaged owingto presence of oxygen during the lye-refining operation. The comparativetest of the stability of the two oils shows further that the timeconsumed during oxidation for attaining a certain peroxide number is 20%longer for the oil refined in a closed system than that refined in anopen system.

EXAMPLE 2 A quantity of rapeseed oil with peroxide number 2.0milliequivalent/l. was refined in a continuously operating all-hermeticrefining system according to the present invention, it being found thatthe peroxide number for the lye-treated, washed and dried oil was 1.8milliequivalent/l. Another quantity of the same oil was deaerated invacuum before refining, and in doing so the oxygen dissolved in the oilwas removed almost completely. From the vacuum tank, the deaerated oilwas pumped to the all-hermetic system without coming into contact withair. The lye-refined, washed and dried oil had a peroxide number of only0.4 milliequivalent/L, i.e. considerably lower than for thenon-deaerated oil and also lower than for the all-hermetically treatedoil mentioned in Example 1, although the peroxide number of crude oilwas considerably higher before refining.

EXAMPLE 3 A quantity of soyabean oil with a content of free fatty acidsof 0.3% and a peroxide number of 2.3 milliequivalent/l. was refined, inone case, in an open system and, in the other case, in an all-hermeticsystem, which were both of the same kind as described in Example 1.

The oils were thereupon bleached in vacuum with 2% bleaching earth at C.and deodorized at 230 C. and 5 mm. Hg. The peroxide number wasdetermined for the lye-treated oils as well as for the bleached anddeodorized oils and, further, the oxidation stability and carbonylcontent of the bleached and deodorized oils were determined. The resultof these tests, which appear from the following Table II, show thatall-hermetically treated oil is superior in every respect to thattreated in S open system (also after bleaching and deodorization) andthat the time consumed for obtaining a certain peroxide number whenoxidizing the deodorized oils is 30% longer for the all-hermeticallytreated oil than for 10 adjustable valve located in the closed linebetween said outlet of the first separator and said pump and its returnline.

11. The combination according to claim 1, in which the oil treated inopen system. said pumping means is a positive pump having a return Thehermetically closed centrifugal separators used in line connecting thepressure and suction sides of the the new system may be any of thewell-known types, pump, said device being a valve located in said returnline such as De Laval Air-Tight separators. and operable to maintainconstant pressure on the suction Table II Analysis of lye- Analysis ofbleached oil Analysis of deodorized oil refined oil Time in Time inPeroxide Peroxide Carbonyl hours for Peroxide Carbonyl hours for numbernumber content attaining number content attaining millimillie. g. at epermillie./g. at the perequi./l equL/l 460 m oxide equi./l 460 mp oxidenumber number 10 Oil refined in open plant 3. 1 0. 33 2.27 158 0.0 1.76175 On refined in all-hermetic plant--- 2. 3 0.28 1. 94 200 0. 0 1. 45230 We claim: side of the pump, the system comprising also means con- 1.The combination of two hermetically closed cennected to the inlet of thefirst separator for supplying feed trifugal separators adapted forcontinuous operation and 5 thereto at a constant rate. adapted to becontrolled independently of each other, 12. The combination according toclaim 1, in which each separator having an inlet and outlets, anhermeticalsaid pumping means is a positive pump having a return lyclosed flow line connecting an outlet of the first sepaline connectingthe pressure and suction sides of the pump, rater with the inlet of thesecond separator, whereby the said device being a valve located in saidreturn line and separators are connected in series, pumping means inoperable to maintain constant pressure on the suction said closed linehaving a capacity at least equal to the side of the pump, the systemcomprising also means conmaximum discharge rate from said outlet of thefirst nected to the inlet of the first separator for supplyingseparator, an adjustable throttle member in an outlet of feed thereto ata constant rate, said last means including the second separator, and adevice operatively connected a closed feed line to said last inlet, apositive feed pump to said closed line for maintaining constant pressurein in said feed line, an adjustable throttle valve in said feed a partof said line. line between said feed pump and the first separator, a

2. The combination according to claim 1, in which said closed returnline connecting the pressure and suction sides device is located tomaintain constant pressure in said of said feed pump, said last returnline leading from the closed line between the first separator and thepumping feed line at a point between the feed pump and said means.throttle valve, a control valve located in said last return 3. Thecombination according to claim 1, in which line and having a valve bodyand a diaphragm operasaid pumping means is a non-positive pump. tivelyconnected to said valve body, the diaphragm partly 4. The combinationaccording to claim 1, in which defining chambers at opposite sides ofthe diaphragm, one said pumping means is a positive pump having a returnof said chambers being connected through the last return line connectingthe pressure and suction sides of the line to the inlet side of saidthrottle valve, and a pipe pump. line connecting the other chamber tothe feed line at the 5. The combination according to claim 1, in whichoutlet side of said throttle valve, whereby said control the adjustablethrottle member is a valve for maintainvalve maintains a constantpressure drop across the inlet ing constant pressure in said outlet ofthe second sepaand outlet sides of said throttle valve. rator.

6. The combination according to claim 1, in which References Cited inthe file of this Pawnt said device is a valve for maintaining constantpres- UNITED STATES PATENTS sure in said outlet of the first separator.

7. The combination according to claim 1, comprising JEddlson g alsovalves in the other outlets of the separators for une maintainingconstant pressure in each of said last outlets, g g g Cummms 1935 8. Thecombination according to claim 1, in which s id 55 P 1940 pumping meansis a positive pump having a return line Lm gren 1941 connecting thepressure and suction sides of the pump, 33 6 gchlosser ig the systemcomprising also a valve located in said return 2346OO5 Bcott Z line andoperable to open in response to a predetermined 2445544 ryson 9 pressuredifierence between the pressure and suction sides Trautman July 19482,502,349 Sebald Mar. 28, 1950 fthepump' 2539 91s L'nd r J 30 1951 9.The combination according to claim 1, in which said 18 g k 1953 pumpingmeans is a positive pump having a return line rezyns connecting thepressure and suction sides of the pump, FOREIGN PATENTS said devicebeing a valve located in said return line and 279 Great Britain Oct. 271927 operagfle to maintain constant pressure on the suction 4 7 5 GreatBritain Dec. 1938 side 0 the pump.

10. The combination according to claim 1, in which OTHER REFERENCES saidpumping means is a positive pump having a return George G. Brown: UnitOperations, John Wiley & line connecting the pressure and suction sidesof the Sons, Inc., New York, pages 298, 299, copyright 1950. pump, saiddevice being a valve located in said return The Sharples Centrifual SoapProcess for the Continuline and operable to maintain constant pressureon the ous Production of Soap, copyright by the Sharples Corp., suctionside of the pump, the system comprising also an Bulletin 1M1.

